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41.
Efficient maritime navigation through obstructions at close range is still one of the many problems faced by mariners. The
increasing traffic densities and average cruise speed of ships also impede the collision avoidance process by reducing the
time available for decision making. This study develops a path-planning algorithm that determines an optimal navigation path
for ships in close-range encounters, using known and predicted data about the traffic and environment. An improved ship dynamic
model has also been developed to better approximate the ship movement under external influences, and the algorithm was evaluated
with a set of test cases simulating various traffic scenarios typically encountered at close range. Since the method is based
on evolutionary algorithm, the algorithm behaviours were evaluated statistically, where properties such as consistency and
practicality of the algorithm outputs are discussed. 相似文献
42.
Demand for commercial air travel has been increasing over the years and recent forecasts indicate similar future trends. New aircraft with enhanced design features are being built and entering the airline service globally. These enhancements aim to ensure continued safety, efficiency, performance and prolonged life serviceability. However, these new enhancements often neglect the impact of the changing anthropometric characteristics of the passenger. Past studies have identified increasing trends in the average weight, height and other anthropometrical and biometrical measures of people at a global scale. However, many are limited to only exploring the ramifications primarily from the perspective of passenger experience. This paper highlights the importance of considering passengers’ anthropometric characteristics from a holistic perspective and identifies gaps for future research. 相似文献
43.
Richard Morris 《Maritime Policy and Management》1993,20(1):67-75
Australia's merchant fleet underwent a delayed response to the trends responsible for the attrition of the OECD fleets over the past decades. A combination of political factors and the heritage of protectionism led to centrally-directed and government-sponsored programmes of modernization. Essentially, compliance with the federal government's shipping policy was achieved through the linkage of reform to tax incentives and to the management of change by tripartite shipowner, government and trade union committees. This paper explores the basic pattern of the reforms, their costings, assessment and policy alternatives. 相似文献
44.
45.
The Southern Ocean is an extreme environment, where waters are permanently cold, a seasonal ice cover extends over large areas, and the solar energy available for photosynthesis is severely restricted, either by vertical mixing to considerable depths or, especially south of the Antarctic Circle, by prolonged seasonal periods of low or no irradiance. Such conditions would normally lead to low productivity and a water column dominated by recycling processes involving microbial components of pelagic communities but this does not seem to be the case in the Southern Ocean, where there is efficient export to large apex predators and deep waters. This paper investigates the role of large microphagous zooplankton (salps, krill, and some large copepods) in the partitioning of biogenic carbon among the pools of short- and long-lived organic carbon and sequestered biogenic carbon. Large microphagous zooplankton are able to ingest microbial-sized particles and thus repackage small, non-sinking particles into both metazoan biomass and large, rapidly sinking faeces. Given the wide spatio-temporal extent of microbial trophic pathways in the Southern Ocean, large zooplankton that are omnivorous or able to ingest small food particles have a competitive advantage over herbivorous zooplankton. Krill efficiently transfer carbon to a wide array of apex predators and their faecal pellets are exported to depth during occasional brief sedimentation episodes in spring time. Salps may be a significant link towards some fish (directly) and other apex predators (indirectly) and, at some locations (especially in offshore waters) and time, they may account for most of the downward flux of biogenic carbon. Large copepods are a trophic link towards fish and at least one whale species, and their grazing activity generally impedes the export of organic particles to depth. As a result, biogenic carbon is channelled mainly towards apex predators and episodically into the deep ocean. Without these original interactions, Antarctic waters might well be dominated by microbial components and recycling processes instead of active export from the generally small primary producers towards large apex predators. 相似文献
46.
This article aims to apply the relationship marketing concept in a professional ship management context. The dramatic growth in the ship management industry means that companies are increasingly seeking ways of ensuring competitiveness. Efforts have mainly concentrated on the improvement of the quality of the service, market entry strategies, establishment in strategic locations, and promotion. Nevertheless, it is argued that in the professional service context of ship management, the aspect of building and maintaining client relationships is of utmost importance. The building of client relationships will require investments of an economic and social nature, training of personnel and the consideration of marketing as a strategic issue. Ship management companies that build long-term client relationships will ensure client retention, reduce transaction costs and achieve differentiation and competitiveness. 相似文献
47.
Richard A. Jahnke 《Journal of Marine Systems》1998,14(3-4)
The response of pore water oxygen, nitrate, sulfate, sulfide, ammonium and methane and particulate organic carbon distributions to the input of 8.5 million m3 (3.8×1012 g) of organic-rich waste materials is simulated. The deposit is assumed to be conical with a maximum thickness of approximately 20 m. Remineralization reactions within the deposit rapidly deplete any initially available pore water oxidants such as oxygen, nitrate and sulfate, and are subsequently dominated by fermentation reactions. Diffusion downward of reduced metabolites, sulfide, ammonium and methane, depletes the available oxidants in the pore waters below the waste pile, increasing the thickness of the anoxic layer. While the impacted region is limited to essentially the deposition site, recovery of the pore waters is estimated to be >104 years. The overall computational results are corroborated by the pore water distributions observed at turbidite boundaries. Numerous uncertainties in the parameterizations limit the overall accuracy of the calculations presented. The most significant of these are: (1) A quantitatively accurate assessment of the remineralization rate of the deposited organic matter including its rate of inoculation by abyssal microorganisms; (2) a detailed assessment of potential non-diffusive pore water transport processes including advection due to compaction and buoyancy-driven flows and enhanced exchange due to macrobenthic irrigation activities and (3) an assessment of the potential alteration of pore space and methane reactivity due to gas hydrate formation. 相似文献
48.
Richard L. Oram 《Transportation》1980,9(4):333-353
Full reliance on conventional forms of bus transit for peak hour needs reduces industry productivity and creates major new subsidy requirements. Restructuring of transit is needed to enable paratransit integration and other innovations than can improve efficiency. This paper discusses the industry's long-term neglect of efficiency and describes subsidy policies that would promote necessary changes. 相似文献
49.
Richard Burroughs 《Maritime Policy and Management》2005,32(3):315-328
Innovation, organizational capabilities, and environmental values combine to determine institutional change for a major marine port. This conceptual framework is applied to the case of dredged material management for the Port of New York and New Jersey. During the century under review, the institutional setting has changed significantly with: (1) environmental considerations moving from nearly irrelevant to central: (2) the number of interests and organizations increasing; and (3) the decision processes becoming far more complex. Ultimately, the new institutional setting influences organizations and individual decisions. As a result of the changes, the practice of dredged material disposal in ocean waters has been limited based on the level of bioaccumulation of selected contaminants. In response to institutional changes, ports requiring deepened channels must rapidly innovate to meet new environmental obligations for material disposal in order to enhance organizational capabilities necessary to maintain competitive advantages in maritime commerce. Successful marine ports will anticipate and meet new societal expectations related to the environment as a condition for continued legitimacy. Collectively these changes imply that ports have moved beyond a carefully circumscribed mission of transportation and economic development to that of a prominent user of coastal space with broad obligations to the public. 相似文献
50.
Several issues concerning the implementation and operation of high-speed rail service in the Detroit-Chicago corridor are identified and discussed in this paper. The primary concern is whether such a service is likely to be attractive enough to induce the private sector to provide it. While the outlook for private operation appears pessimistic, consideration of a broader range of potential benefits (e.g., direct and indirect employment) may justify public involvement and investment. 相似文献